German firms apply data-driven reactor dismantling amid mounting closures

ENBW's Neckarwestheim-1 reactor has become the latest German plant to commence dismantling and contractors are using software to optimize the removal of radioactive materials ahead of a national decommissioning surge.

Decommissioning work on EnBW’s 840 MW Neckarwestheim-1 plant (GKN I) was set to start this month after the Baden-Wurttemberg environment ministry granted the German operator a dismantling permit February 3, EnBW said in a statement.

ENBW stopped the Neckarwestheim 1 reactor (PWR) in 2011, along with its 926 MW Philippsburg 1 Boiling Water Reactor (BWR). Both units are in post-operation status. ENBW stopped its 357 MW Obrigheim PWR plant in 2005 and the unit is currently undergoing decommissioning. The operator plans to close its 1.5 GW Phillipsburg 2 and 1.4 GW Neckarwestheim 2 plants in 2019 and 2022, respectively.

EnBW estimates the dismantling of Neckarwestheim-1 will take ten to 15 years. Dismantling work on the main coolant lines around the RPV will be conducted first, in parallel with preparations to dismantle the internals.

ENBW began building the dismantling plan for Neckarwestheim-1 in 2011 and these were submitted to the regulatory authorities in 2013. A four-year consultation and review process was completed this year.

“We are pushing ahead with the creation of a suitable infrastructure for efficient dismantling in Philippsburg and Neckarwestheim and have been building residual processing centres at both sites since the beginning of 2016,” Jorg Michels, Managing Director of EnBW Kernkraft GmbH, said in the February 3 statement.

Rising activity

The number of Decontamination and Decommissioning (D&D) projects in Europe is expected to rise 8% per year in the coming decade as low power prices dent operating profits and plants reach end of lifespans, Jorg Klasen, ENBW’s Director Nuclear Decommissioning Services at German operator EnBW Kernkraft, said in May 2016.

The number of reactors in decommissioning is expected to rise from 76 in 2015 to around 110 in 2020, Klasen said.

Germany’s federal government has ordered all nuclear power plants to close by 2022, and decommissioning activity will spike around this date, Jorg Viermann, Head of Sales Waste Management at Gesellschaft fur Nuklear-Service (GNS), told Nuclear Energy Insider. GNS supplies spent fuel casks and other decommissioning services.

“We will have up to ten plants to dismantle and decommission in parallel and that is a large opportunity, especially for companies from abroad because there is not enough capacity in Germany,” Viermann said.

                                    Germany's nuclear power plants

Source: World Nuclear Association (WNA)

Vessel analysis

In 2015, GNS won a contract to dismantle the reactor pressure vessel (RPV) and internals at Philippsburg 1, as part of a Westinghouse-led consortium that also included Nukem Technologies.

GNS works with contractors to calculate the level of radioactivity of segmented RPV materials and plan the storage capacity to accommodate the waste. The company has developed a digital modelling solution that maps neutron-induced activation of RPV components, as well as that of external field structures, Prof Peter Phlippen, Head of Calculations at Wissenschaftlich-Technische Ingeniuerberatung (WTI), a subsidiary of GNS, said. The program was first used by GNS on the Philippsburg I BWR reactor.

Accurately calculating the overall volume of waste generated from dismantling an RPV and its internals is relatively straightforward using original NPP plans, but calculating the volume of radioactive material for different levels of radioactivity is more challenging.

GNS’ program integrates widely-available software, such as Monaco and MCMP, to process material composition data for each component of the RPV, Phlippen said.

The operator collects the data over a month and WTI then takes around two months to perform the modelling and calculations. The program can include ad hoc information such as undocumented material changes to improve the accuracy of the calculations.

Fewer casks

The GNS modelling can improve the safety of the decommissioning process and allow more efficient and realistic packaging strategies, Dr Luc Sclomer, Group Leader Nuclear Calculations at WTI, said.

Improved accuracy of waste material classification allows decommissioning companies to use fewer storage casks and this is the “real cost saving” of the software, Sclomer said. The WTI model analyses the whole waste management cycle, so final storage costs are also optimised, he said.

GNS supplies a range casks tailored for packing different waste and the company also operates an Interim Storage Facility in Lower Saxony, which will be handed over to the Federal Government later this year.

German storage capacity will be boosted in around 2022, when the Konrad mine final repository in Salzgitter is due to enter into operation.

By Karen Thomas